Force-sensing catheter with bonded center strut

Abstract

A force-sensing catheter for diagnosing or treating the vessels found within a body or body space includes a center strut that is bonded, preferably thermally, along its longitudinal axis with the thermoplastic tubular member within which it is housed. The tubular member preferably has three layers: an inner layer, a braided layer and an outer layer. One or more semiconductor or metallic foil strain gages are affixed to the center strut in order to provide a measure of the bending and torsional forces on the distal tip of the catheter. Temperature compensation is achieved by having a temperature sensor near the strain gages and calibrating the catheter over a range of temperatures.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a medical device for use in the vessel of a patient for the purpose of diagnosing or treating the patient, such as mapping tissue and / or ablating tissue using radio frequency (RF) or other sources of energy. More particularly, the invention relates to a catheter having a center strut bonded into the catheter tip to define an inseparable composite tip structure that maximizes the open internal volume of the catheter tip and the torsional rigidity of the catheter tip while minimizing the outside diameter of the catheter tip and providing uniform on-plane tip deflection. On the bonded center strut one or more strain gage force sensors are affixed for measuring catheter tip deflection and tip axial and side forces. The catheter may also include puller wires for deflecting the tip portion of the catheter.BACKGROUND OF THE INVENTION[0002]Many abnormal medical conditions in humans and other mammals have been associated with disea...

AI Technical Summary

Benefits of technology

[0015]This composite tip structure provides two enclosed, large diametrically-opposed, half moon shaped lumens extending through the tip providing space for wiring, sensors, fluid carrying tubing and the like. The strut separating the half moon shaped lumens can be constructed from any of a number of superelastic (metallic) alloys such as nitinol, beta titanium or spring tempered stainless steel. This composite catheter tip design maximizes the cross-sectional area of the open lumens in the catheter tip and torsional rigidity of the catheter tip while minimizing the outer diameter of the catheter tip by providing a single uniform area moment of inertia at any cross section of the catheter tip the longitudinal axis because the bonded center strut and elastomeric tube are not allowed to move with respect to each other during tip deflection. This composite structure provides uniform on-plane tip deflection and uniform torque and deflection forces regardless of the tip deflection angle because the tip cross-sectional area moment of inertia remains constant along the entire tip length during tip deflection. All known prior art tip designs exhibit varying cross-sectional area moments of inertia during tip deflection because the inner strut and outer elastomeric tube are fixed to each other only at their proximal and distal end locations and the strut and outer tube move with respect to each (other) during tip deflection. In all prior art designs, the combined centroidal axis of the independently moving strut and outer tube is continuously variable during tip curvature since the absolute distance between the centroidal axis of the whole (strut and outer tube) and the centroidal axis of each of the parts is variable. This produces non-uniform torque and deflection forces that are dependent on the degree of tip curvature.

[0016]The deflection curve profile of the catheter tip can be modified by varying the area moment of inertia of the strut cross section perpendicular to the struts longitudinal axis by utilizing cutting or coining operations that either remove material or change the material thickness in various portions of the center strut cross section. The composite deflecting tip with a bonded center strut has a large width to thickness ratio thus providing a first centroidal axis that has a large area moment of inertia and a second corresponding low area moment of inertia about a centroidal axis orthogonal to the first centroidal axis thereby providing exceptional on-plane deflection characteristics.

[0017]The present invention provides a single unified high-performance composite structure for the deflecting tip assembly of a deflectable catheter that combines the properties of elastomers and metals and eliminates extruded core lumens. The two half-cylindrical lumens created by the bonded strut provide a large volume in which to place wiring, tip force and location sensors and tip irrigation lumens. Alternatively, an intermediate portion between the deflectable tip section and the tip electrode can be provided in which there is no center strut and which provides even greater room for temperature and location sensors. Catheter tip diameters can be reduced since the working volume of the tip lumen is maximized with this design.

[0020]The distal end of the center strut comprises at least one snap-fit notch and the molded coupling further comprises at least one snap-fit wedge adapted to receive the snap-fit notch. This construction enables the rapid assembly of the tip electrode and the composite tubular member and center strut.

Problems solved by technology

While this patent discusses the use of such sensors for measuring and depicting the bend of the catheter to the user it does not provide a means for accurately providing force sensing at the tip of the catheter.

U.S. Pat. No. 6,612,992 to Rambow et al. discloses an ultrasound catheter that uses a plurality of strain gages placed along the periphery of the catheter to provide information regarding the position of the catheter in the cardiovascular system, however, there is no teaching with respect to sensing the force at the tip of the catheter.

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